OpenShift 3.7 Upgrade Extended Builds (Technical Preview) replacement

Extended Builds, which were Technical Preview prior to 3.7 have been dropped.

Advantages of chained builds over extended builds that lead to this decision:

• Supported by both docker and s2i build strategies, as well as combinations of the two, compared with s2i strategy only for extended builds.
• No need to create/manage a new assemble-runtime script
• Easy to layer application components into any thin runtime-specific image

References

• https://github.com/openshift/origin/pull/16811/files
• https://docs.openshift.com/container-platform/3.7/dev_guide/builds/advanced_build_operations.html#dev-guide-chaining-builds
• https://blog.openshift.com/chaining-builds/